1. Field of the Invention
The present invention relates to a moving-magnet, linear motor, an aligner provided therewith, and a method for manufacturing devices, for example, semiconductor devices, using the aligner.
2. Description of the Related Art
In various types of equipment, such as machine tools and semiconductor manufacturing apparatuses, linear motors have been used to achieve accurate positioning control. In machine tools, semiconductor manufacturing apparatuses, and the like, in addition to achieving accurate positioning control, linear motors are required to produce a large thrust force for improving productivity and to have a light-weight mover.
FIGS. 9A, 9B, and 9C are a top view, a side view, and an illustration of the configuration of a known moving-magnet, linear motor, respectively, by way of example. The linear motor includes a stator 800 and a mover 810. The stator 800 includes a base 801, a toothed-armature, iron-core 802 (sometimes referred to herein as xe2x80x9ctoothed iron-corexe2x80x9d and iron-core) having a plurality of teeth, and a plurality of coils 803 respective coils of which are wound around respective teeth 802a of the iron-core 802. The iron-core 802 and the plurality of coils 803 are fixed on the base 801. The mover 810 has magnet rows, i.e., magnet units, formed of a plurality of permanent magnets 811, which are orderly disposed along the traveling direction of the mover 810, i.e., in the thrust direction of the linear motor, so as to face the upper surface of the stator 800 with a gap therebetween, and a back yoke 812 so as to provide an improved magnetic flux coupling (hereinafter, referred to as xe2x80x9cflux linkagexe2x80x9d) of the rows of the magnets with the coils 803. The mover 810 is fixed to a stage (not shown) guided by a guide (not shown) and the stage is driven in the thrust direction of the linear motor.
The coils 803 along with the iron-core 802 allow the linear motor to produce a large thrust force.
Also, in the linear motor, the mover 810 is formed of magnet units so as to have a light weight. If the mover 810 is formed of coil units, the greater the number of wire turns, that is, the heavier the weight of the coils on the mover 810 so as to produce a larger thrust force, the heavier the mover 810 becomes. On the contrary, the number of wire turns, that is, the weight of the coils 803 fixed to the base 801 of the stator 800 is irrelevant to the weight of the mover 810 formed of magnet units.
In the linear motor, the length of 11 magnets 811 is equal to those of 12 stator iron-core teeth 802a and 12 stator iron-core slots 802b in the traveling direction of the mover 810. These 12 teeth 802a and 12 slots 802b form a unit of the linear motor having a three-phase configuration. That is, this linear motor has a so-called xe2x80x9c11-pole, 12-slot configurationxe2x80x9d.
The stator coils 803 are connected so as to form a three-phase configuration, i.e., a U, V, and W phase configuration. The two adjacent coils in each phase are connected either in series or in parallel.
In the linear motor shown in FIGS. 9A to 9C, the stator 800 has 36 slots 802b forming three units of three U, V, and W phase configurations. For ease of understanding, the coils in the U phase are taken as an example, and the coils in the first, second, and third units are referred to as U1, U2, and U3 coils, respectively. The U1 to U3 coils are connected to each other either in an in-phase or an opposite-phase mode with respect to the electrical degrees thereof, and are energized only when they face the magnets 811. That is, the U1 to U3 coils are switched over in accordance with the travel of the magnets 811. The foregoing discussion also applies to the coils 803 in the V and W phases.
The magnet rows have 14 poles, that is, 14 magnets. Among these 14 magnets, 11 magnets mainly contribute to producing a thrust force, and the remaining 3 magnets are provided so as to switch over the coils 803.
FIGS. 10A to 10J illustrate the positional relationships between the moving magnets 811 and the coils 803 to be energized. In these figures, the coils 803 marked x are to be energized. In this linear motor, basically, although no two pairs of coils 803 in the same phase are energized at the same time, the two pairs of coils 803, i.e., 4 coils=2 coilsxc3x972 pairs, are energized at the same time when these coils 803 face the moving magnets 811 at the same time. However, these coils are not energized at the instant of switch-over. The energizing currents are controlled by using sinusoidal currents so as to make the vectors of the flux linkages orthogonal to the vectors of the currents. This control is generally known as xe2x80x9csinusoidal drivingxe2x80x9d. The linear motor produces a thrust force by performing the sinusoidal driving and the switch-over of the coils at the same time.
Although the U1 to U3 coils are connected either in an in-phase or an opposite-phase mode to each other in the previous explanation, the U1 and U3 coils are connected in an in-phase mode to each other, and are in an opposite-phase mode with respect to the U2 coils in this example, because the linear motor has a configuration formed of 11 poles and 12 slots and the number of the poles is odd. Since one pole corresponds to 180 electrical degrees (180xc2x0), when the number of poles is odd, the three-phase coils in a unit are in an opposite-phase mode with respect to the corresponding three-phase coils in the neighboring unit.
The linear motor provided with the iron-core produces a so-called xe2x80x9ccogging forcexe2x80x9d caused by an attractive force between the permanent magnets and the iron-core. The cogging force occurs regardless of the existence of the energizing current, and deteriorates the positioning accuracy of the linear motor. Also, the cogging force requires additional energizing current for the linear motor to produce a necessary thrust force and thereby causes the amount of heat produced by the linear motor to increase.
To solve these problems, some methods have been proposed. For example, the moving magnets may have an additional compensation pole so as to compensate for an apparent cogging force, and a plurality of linear motors may be used so as to shift the phases of the coils of one linear motor from those of the corresponding coils of the other linear motors. However, these methods only remove specific harmonic components of the cogging force and have not managed to completely eliminate the cogging force, including the harmonic components thereof.
The present invention has been made in view of the above-described background. Accordingly, it is an object of the present invention to provide a moving-magnet, linear motor, which has reduced cogging force, preferably nearly zero.
In accordance with a first aspect of the present invention, a moving-magnet, linear motor comprises a mover and at least one stator. The mover comprises a plurality of permanent magnets orderly disposed along the traveling direction thereof. The stator comprises a toothed iron-core with a plurality of teeth and a plurality of coils wound around the teeth of the iron-core. The two longitudinal ends of at least one permanent magnet among the plurality of permanent magnets are skewed with respect to each other substantially by a positive, integral multiple of a tooth pitch of the toothed iron-core.
Also, another moving-magnet, linear motor comprises a mover and at least one stator. The mover comprises a plurality of permanent magnets orderly disposed along the traveling direction thereof. The stator comprises a toothed iron-core with a plurality of teeth and a plurality of coils wound around the teeth of the iron-core. A cogging force produced by at least one permanent magnet among the plurality of permanent magnets has a phase changing from 0 to 360 degrees (0xc2x0 to 360xc2x0) in a continuous or multistep manner along the length direction of the permanent magnet.
In the moving-magnet, linear motor according to the present invention, each permanent magnet may have a shape, which is approximately a shape of parallelogram, or another polygon.
In the moving-magnet, linear motor according to the present invention, the length of each permanent magnet is preferably equal to or smaller than the width of the toothed iron-core, wherein the length of each permanent magnet and the width of the iron-core extend in a direction orthogonal to the traveling direction of the moving magnets.
In the moving-magnet, linear motor according to the present invention, a tooth pitch of the toothed iron-core is preferably equal to or smaller than a magnet cycle of the permanent magnets.
The moving-magnet, linear motor according to the present invention, the foregoing at least one stator may comprise two stators disposed so as to sandwich the mover therebetween.
In accordance with a second aspect of the present invention, an aligner for exposing a pattern formed on an original plate onto a substrate comprises at least one driver for driving at least one of the original plate and the substrate. The driver includes the moving-magnet, linear motor according to the first aspect of present invention. For example, the foregoing moving-magnet, linear motor is applied to at least one of drivers for driving an original plate stage, i.e., a reticle stage, and a substrate stage, i.e., a wafer stage.
In accordance with a third aspect of the present invention, a semiconductor manufacturing apparatus, or a machine tool, comprises at least one driver including the moving-magnet, linear motor according to the first aspect of the present invention.
In accordance with a fourth aspect of the present invention, a method for manufacturing devices, in particular semiconductor devices, comprises the steps of (1) applying a photosensitive agent on a substrate, (2) exposing a pattern on an original plate onto the substrate having the photosensitive agent applied thereon, and (3) developing the substrate having the pattern exposed thereon. The aligner according to the second aspect of the present invention is used in the exposing step.
Further objects, features, and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.